Buffett told CNBC he hadn't made the decision, but that "one of the fellows in the office that manage money" bought shares of Amazon.
The comments pointed to Todd Combs or Ted Weschler, each of whom manages portfolios for Berkshire Hathaway, CNBC reported.
"Yeah, I've been a fan, and I've been an idiot for not buying" Amazon shares, Buffett said. "But I want you to know it's no personality changes taking place."
Berkshire Hathaway also owns about 250 million shares in fellow tech giant Apple (AAPL) . making Berkshire the second-largest shareholder in the iPhone maker.
Berkshire is slated to report first-quarter earnings on Saturday. The company will file its quarterly update on details of its portfolio holdings later this month with the Securities and Exchange Commission.
Amazon shares were rising 2% on Friday to $1,939.28. The stock has risen 29% so far in 2019.
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